Concrete Stair design approach

[Anonymous]

Hello all,

I have this simple concrete set of stairs that I need to run an engineering analysis to see how the slab performs and if the suggested reinforcement work. The question I have is quite basic and has to do with modelling the structure. Please refer to the image below:

The above stair way is attached (bearing) on the existing foundation wall below. Some of the questions I have are:

1. How would I model the landing? (I'm thinking of using the floor/panels option)

2. How would I model the steps? (Should I model them individually or as a ramp? How will I be able to generate reinforcement for the steps?)

3. How should I model the new foundation walls, and strip footings? (Can I model them all together or should I model them separately?)

As for the landing, there is a peculiar case. Please see the next image:

The hatched portion of the slab shows the area where the slab thickness reduces for it to bear on the existing foundation wall. Questions are:

4. Do I model that small portion separately and connect the 2 slabs using rigid links? (What would be the best approach in this?)

5. Is it possible to extract information at that location? (i.e. stresses experienced at the point where the slab reduces in height?)

Thank you.

[saclovitzky]

Hello,

Model the landing/stair as slab element(shell), do not model the steps(just take them as dead load,ie, if the height of thread = 175, then, DL =1/2(.175)(25) ).

As a general rule, keep your model as simple as possible.

hope this helps.

[Anonymous]

Hi Saclovitzky,

I agree that keeping the model simple would be ideal but If I do not model the steps, then I wouldn't be able to obtain any reinforcement for them. Also, I'd like to hear your input on the other questions I've posted if possible.

[Rafacascudo · Accepted solution]

I don't think Robot concrete design will provide step reinforcement.
But I can be wrong

[Artur.Kosakowski · Accepted solution]

It will not.

[saclovitzky · Accepted solution]

Hello,

Looking at your section, you can design your stair and landing as simply supported(pls. see attached).

Regarding, the reduced depth on the support of landing,you can ignore that since the half-joint support is located below(if it is located on the upper portion, that's another issue and you need to check the adequacy of the reduced depth),provided you have a minimum ,ie, 100mm bearing distance.

Normally, you do not design reinf for the steps but rather provide "min reinf(ie,H10@200)" since the bulk of the reinf is already accounted for on the bottom reinf. of the "waist".

Hope this helps.

[Simau]

Hi,

As told before, keep the model as simple as possible.

Attached is a principle of reinforcement sketch

[Anonymous]

Helpful Article thanx for sharing